KR20150123882A - Process for producing 2-propylheptyl acrylate by transesterification - Google Patents

Abstract

The present invention relates to industrial production of high purity 2-propylheptyl acrylate in a high yield by a transesterification method, which is preferably a semi continuous mode. The process according to the invention is to carry out a purification sequence comprising a single distillation column and a film blower using ethyl titanate in a solution of 2-propylheptyl titanate or 2-propylheptanol as the transesterification catalyst.

Description

PROCESS FOR PRODUCING 2-PROPYLHEPTYL ACRYLATE BY TRANSESTERIFICATION BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing 2-propylheptyl acrylate by transesterification,

The present invention relates to the production of 2-propylheptyl acrylate by a semi-continuous transesterification process.

It is known that a trans esterification reaction between a hard alkyl acrylate (known as a hard acrylate) and a heavy alcohol is performed to produce an acrylate ester.

The reaction is an equilibrated catalytic reaction involving the production of a light alcohol according to formula (I).

It is necessary to remove the light alcohol produced during the reaction for the equilibrium movement in the production direction of the acrylic acid ester.

This reaction usually involves side reactions that generate impurities and it is necessary to remove the impurities to obtain a high purity acrylic ester that meets the technical requirements related to the end use as monomers for preparing polymers usable in various fields of application.

Furthermore, for obvious economic reasons, the crude reaction mixture, particularly the unreacted reactants and the products of economic value present in the catalyst, are recycled as possible during the process.

For these purposes, a separation / purification process comprising a combination of distillation, extraction and / or separation by settling is usually carried out which results in a relatively complex and energetic side effect, Is expensive.

The applicant company has been particularly interested in the synthesis of 2-propylheptyl acrylate (alkyl acrylate having C ₁₀ branched chain) from hard acrylate and 2-propylheptanol (known as 2-PH) In the field of paints, inks and adhesives, the monomers may exhibit advantageous effects.

According to the document JP05-070403, according to a method known to a person skilled in the art, by transesterification of 2-propylheptanol with a light acrylate such as methyl acrylate in the presence of p-toluenesulfonic acid and a polymerization inhibitor as a catalyst, To obtain 2-propylheptyl acrylate. The methanol formed is subsequently removed and is followed by a sublimable distillation followed by purification of the resulting reaction product after the reaction. JP05-070403 Literature does not explicitly mention the purification level to be carried out or the purity level required for the monomer for its use.

Various transesterification methods for the production of C ₂ -C ₁₂ alkyl acrylates have already been described in the prior art.

For example, it is possible to mention US 7 268 251, which treats a reaction effluent stream from transesterification in the following manner:

. Most of the objective acrylic acid esters were first all separated and then isolated from the catalyst used for distillation (catalyst separation)

. Alternatively, the used catalyst is firstly separated by distillation (catalyst separation), then most of the acrylic acid ester is separated,

. Then, a compound having a boiling point lower than that of the objective acrylic acid ester is separated from the obtained mixture by distillation (low boiling point substance separation), followed by distillation of the acrylic acid ester (distillation in a pure state).

This method requires the use of four or more distillation or rectification columns, including an evaporator, for catalyst separation, which is generally titanium alkoxide.

The process described in US 7 268 251 relates to the preparation of alkyl acrylates by transesterification starting from alcohols having chain lengths longer than that of alkyl acrylates and starting acrylates by one or more carbons, This method relates only to the production of dimethylaminoethyl acrylate from methyl acrylate or ethyl acrylate and dimethylaminoethanol in two successive reactors.

The process described in US 7 268 251 is unsuitable for the implementation of industrial scales for obtaining products with high purity and satisfactory productivity, because of the optimization of the operating conditions of the four distillation / rectification component sequences.

US 6 977 310 discloses a continuous process for the preparation of (meth) acrylic acid alkyl esters from methyl (meth) acrylates and C ₂ -C ₁₂ alcohols in the presence of tetraalkyl titanates as transesterification catalysts. The process comprises subjecting the reaction mixture to crude distillation to separate readily volatile compounds (unreacted reactants); Followed by transferring the resultant fraction leaving the bottom of the column containing the resulting ester, catalyst, polymerization inhibitor and high boiling point byproduct to the vacuum distillation stage. This vacuum distillation step comprises a film evaporator combined with a distillation column in particular for complete removal of the high boiling point product in the resulting ester. The resulting ester is recovered at the top with high purity.

According to the process, only the preparation of butyl methacrylate or isobutyl methacrylate is illustrated and the desired methacrylate is removed from the bottom stream from the first column for reduced pressure distillation Occurs.

Prior art methods use alkyltitanates such as tetraethyl titanate, tetrabutyl titanate, or tetra (2-ethylhexyl) titanate as the transesterification catalyst, and examples thereof include trans-ester of propylheptanol and light acrylate By the esterification reaction, it is not directly applied to long-chain alkyl acrylates such as 2-propylheptyl acrylate. This means that the transesterification of the light alcohol (ethanol or methanol) or the starting 2-propylheptanol and the titanate released during the reaction is achieved by reacting butyl acrylate or 2-ethylhexyl acrylate with the reaction mixture or the light ester / Which causes the appearance of the same impurities, complicating the purification of 2-propylheptyl acrylate.

The Applicants have attempted to solve the problems associated with the use of 2-propylheptanol in the various problems of the process, in particular trans-esterification reactions catalyzed by alkyl titanates, Propylheptyl acrylate at high purity and high yield, including the recycle of the product with high yield and high yield, comparable to industrial scale production.

The solution provided is to use a purification line comprising only one distillation column and a film evaporator, using ethyl titanate in solution in 2-propylheptyl titanate or 2-propylheptanol as the transesterification catalyst.

The inventors have also found that trans-esterification with a tin derivative as a transesterification catalyst, especially tin dibutyl tin oxide, also being able to overcome the problems of the above methods and comprising only a single distillation column and a film evaporator, Was found to be usable for the preparation of 2-propylheptyl acrylate.

The subject of the present invention is a process for the production of 2-propylheptyl acrylate by transesterification of a light alkyl acrylate and 2-propylheptanol in the presence of an alkyl titanate as a transesterification catalyst and at least one polymerization inhibitor, In order to obtain high purity 2-propylheptyl acrylate, an azeotropic mixture composed of a light alkyl acrylate and a light alcohol produced by a trans esterification reaction is withdrawn continuously during the reaction, and the reaction mixture is purified , The method characterized by:

- The catalyst is selected from ethyl titanate and 2-propylheptyl titanate in a 2-propylheptanol solution;

- Objective 2-Propylheptyl acrylate was reacted with unreacted light alkyl acrylate as a light product and a minor amount of 2-propylheptanol and a crude reaction mixture comprising a catalyst as a heavier product, polymerization inhibitor (s) Transferred to distillation column (C1) under reduced pressure, and distillation is carried out in said column (C1) to obtain

o At the top, a stream consisting essentially of unreacted light alkyl acrylate and a minor amount of 2-propylheptanol, and

o At the bottom, a stream consisting essentially of the desired 2-propylheptyl acrylate and catalyst, polymerization inhibitor (s), also the heavy reaction by-products, and traces of the hard compound; after

- The downstream stream from the distillation column (C1) is transferred to a film evaporator under reduced pressure to make it possible to:

o At the top, the desired pure 2-propylheptyl acrylate; And

o In the bottom, the catalyst, polymerization inhibitor (s), and also heavy reaction by-products.

In the present invention, "hard alkyl acrylate" or "hard acrylate" has the same meaning, which means an acrylic acid ester containing a short alkyl chain, i.e. a linear C ₁ -C ₄ alkyl chain, C ₁ -C ₄ alcohols.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the present invention, which is not intended to be limited by the following description, with reference to the single attached drawings, which schematically illustrate a plant that enables the practice of the method according to the present invention.

The process for preparing 2-propylheptyl acrylate according to the present invention may be a batch process, a continuous process, or a semi-continuous process, i.e. the reaction part may be batchwise and the purification part may be continuous. Preferably, the method of the present invention is semi-continuous.

The alcohols, 2-propylheptanol, used in the process of the present invention are represented by the form C ₅ H ₁₁ CH (C ₃ H ₇ ) CH ₂ OH and the C ₅ H ₁₁ group is represented by nC ₅ H ₁₁ , C ₂ H ₅ CH (CH ₃₎ may represent a CH ₂ or _{CH 3 CH (CH 3) CH} 2 CH 2.

The abbreviation of 2-PH on a continuous substrate is understood to mean 2-propylheptanol, in the form of each of the isomers, either alone or in mixture. 2 -PH is another isomeric low content such as 2-isopropylheptanol, 2-isopropyl-4-methylhexanol, 2-isopropyl-5-methylhexanol or 2-propyl- .

2-PH can be prepared in a variety of ways, for example, by aldolization of n-valeraldehyde prepared by hydroformylation of butene and dehydration of the alcohol obtained to give 2-propyl-heptanol and subsequent hydrogenation .

2-PH can also be obtained by condensation of 1-pentanol (in the form of a methyl butanol mixture) in the presence of KOH at elevated temperatures according to the Guruber reaction.

In the present invention, 2-PH predominantly comprises 2-propylheptanol.

Generally, 2-PH is a mixture comprising:

- 70 to 99%, preferably 80 to 95% of 2-propylheptanol n C ₅ H ₁₁ CH (C ₃ H ₇ ) CH ₂ OH and

Methyl-2-propyl-hexanol C ₂ H ₅ CH (CH ₃ ) CH ₂ CH (C ₃ H ₇ ) CH ₂ OH and 5-methyl- 2-propyl hexanol _{CH 3 CH (CH 3) CH} 2 CH 2 CH (C 3 H 7) CH ₂ OH in the mixture.

2-Propylheptanol is especially marketed by BASF.

As the hard alkyl acrylate used as a starting material in the method of the present invention, methyl acrylate, ethyl acrylate or butyl acrylate, preferably ethyl acrylate, is used.

The hard alkyl acrylates are obtained by direct esterification of acrylic acid, which is industrially produced from propylene essentially with light alcohol, usually methanol, ethanol, or butanol.

In particular, the present invention relates to a process for dehydrogenating glycerol and a process for producing acrolein from acrolein, and a process for the subsequent vapor phase oxidation of acrolein obtained therefrom, or a process for dehydration of 2-hydroxypropionic acid (lactic acid) or 3-hydroxypropionic acid and an ester thereof Lt; RTI ID = 0.0 > acrylic acid < / RTI > derived from a renewable source of acrylic acid.

The invention also applies to the use of light alkyl acrylates derived from alcohols of biological sources such as bioethanol.

Typically, the transesterification reaction is carried out in the presence of an excess of a hard alkyl acrylate, especially in the presence of a hard alkyl acrylate / 2-PH molar ratio of from 1 to 3, preferably from 1.3 to 1.8, with an external exchanger equipped with a distillation column This is carried out in a stirring reactor (A).

The transesterification catalyst is ethyl titanate in a solution of 2-PH, for example, a 90% solution of ethyl titanate in 2-PH or a 2-propyl titanate obtained by previously reacting 2-PH and ethyl titanate at 100 ° C. Heptyl titanate; Preferably, ethyl titanate in solution in 2-PH is used.

The invention also applies to the use as a transesterification catalyst of tin derivatives such as dialkylated tin salts of linear or branched alkyl chains of 1-8 carbon atoms. By way of example, mention may be made of dialkyltin dilaurates having an alkyl chain of from 1 to 4 carbon atoms, i.e. dimethyl tin oxide, diethyl tin oxide or more particularly di (n-butyl) tin oxide (DBTO).

The catalyst is used in a ratio of 5.10 ^-4 to 5.10 ^-2 mol per 2-PH mol, preferably 10 ^-3 to 10 ^-2 mol per 2-PH mol.

The transesterification reaction is usually carried out in reactor (A) at a pressure of 200 mmHg (0.27 x 10 < ⁵ > Pa) to atmospheric pressure and a temperature range of 90 [deg.] C to 130 [deg.] C,

The reaction is carried out under at least one polymerization inhibitor which is introduced into the reactor at a rate of 10 to 5000 ppm, preferably 200 to 1000 ppm, with respect to the crude reaction mixture.

Examples of polymerization inhibitors that can be used include phenothiazine, hydroquinone, hydroquinone monomethyl ether (HQME), di (tert-butyl) -para-cresol (BHT), TEMPO (2,2,6,6- Di (tert-butyl) catechol or TEMPO derivatives, such as 4-hydroxy-TEMPO (4-OHTEMPO) and mixtures of these alone or in all ratios. Preferably, hydroquinone monomethyl ether (HQME) is used as the polymerization inhibitor.

The supplemental addition of the polymerization inhibitor is usually carried out in a distillation column equipped in the reactor, in a subsequent purification treatment, in particular in the distillation column (C1), and in the downstream stream end product of the upper condenser of the film evaporator.

The light alcohol (usually methanol or ethanol) formed by the transesterification reaction is continuously discharged in the form of an azeotropic mixture with the light alkyl acrylate by distillation in the column mounted in the reactor. Advantageously, the mixture is recycled to the light acrylate synthesis unit. The synthesis unit proceeds according to the direct esterification of the light alcohol and acrylic acid.

After a reaction to the residence time in the reactor of usually 3 to 6 hours, the crude reaction mixture 5 is mixed with the objective 2-propylheptyl acrylate, the unreacted hard alkyl acrylate as the hard product and the trace 2-HP, , Polymerization inhibitor (s), and also heavy reaction by-products.

When the reaction is carried out in a semi-continuous manner, the reaction mixture is stored in the buffer tank B before the purification treatment.

The purification treatment was carried out in a separate fraction, comprising distillation column (C1), and a film evaporator, in which the air was sent downwards, also known to the person skilled in the art, usually as stripping column, with pure 2-propylheptyl acrylate, To obtain a catalyst, polymerization inhibitor (s) and heavy reaction by-products.

The distillation column (C1) is usually operated under a pressure range of 10 to 50 mmHg (0.013 x 10 ⁵ Pa to 0.067 x 10 ⁵ Pa) at a lower temperature range of 90 to 150 ° C.

The overhead stream 7 from the distillation column (C1) consists mainly of unreacted hard alkyl acrylate and a minor amount of 2-PH.

The stream 7 is preferably condensed and recovered to be recycled to the transesterification in the reactor (A). However, the stream present in small quantities can be simply disposed of through the column for vent wash, into the aqueous discharge stream from the process.

The bottoms stream 8 from column C1 consists primarily of the desired 2-propylheptyl acrylate, the catalyst, the polymerization inhibitor (s), and the heavy reaction by-products, and can contain the remaining amount of light compounds (unreacted reactants).

The stream 8 is sent to a film evaporator (E) for catalyst separation from the finished product, and the separation of the catalyst in the "stripped " mixture does not require the use of a distillation column. The purified 2-propylheptyl acrylate 9 is separated from the upper portion and the fraction 10 containing the catalyst, polymerization inhibitor (s) and heavy reaction by-products is separated from the bottom.

Part 11 of stream 10 is optionally recycled to the reaction in reactor (A) and the remainder is disposed of and incinerated to prevent excessive accumulation of heavy byproducts in the reactor.

As a film evaporator, a falling film evaporator or a wiped film evaporator can be used in particular. This type of evaporator offers the advantage of a reduced residence time which limits the formation of additional heavy compounds downstream of the reaction section. The evaporator essentially consists essentially of a cylinder portion heated by a jacket, a top portion used for vapor separation, and a rotor rotating at high speed. The stream to be treated is dispersed on the entire heating surface in the form of a high turbulent film. The formed vapor rises in a direction opposite to the flow toward the top of the apparatus. Essentially, the non-volatile products, which are catalyst, polymerization inhibitors and heavy reaction by-products, reach the bottom of the evaporator and are released in the form of stream 10. The gas stream 9 above the evaporator is made up of the purified desired product.

The film evaporator operates at a pressure of 10 mbar and a temperature of 160 ° C.

The process for preparing 2-propylheptyl acrylate of the present invention seeks for 2-propylheptyl acrylate with a purity of more than 99.5% and shows productivity comparable to industrial scale production, and in particular, for example, adhesives, coatings, With respect to the possibility of using said monomers in the preparation of latexes with low content volatile organic compounds in the field.

Experimental part

In the examples, percentages are by weight unless otherwise indicated, and the following abbreviations are used:

EA: Ethyl acrylate

2-PH: 2-propylheptanol

2PHA: 2-propylheptyl acrylate

HQME: Hydroquinone methyl ether

Example 1 (according to the invention)

(2-PH, stream 1), 490 g of ethyl acrylate (EA, stream 2), and 2-PH (85% mixture of 2-PH) with air injection for stabilization of the reaction medium. ) Solution and 0.13 g of HQME (stream 3) in a solution of ethylenediamine were heated in a thermosiphon type external exchanger equipped with a Multiknit type stacked packed distillation column with 12 theoretical plates, The stirred 1L reactor A is charged. A mixture containing 500 ppm of HQME in EA is introduced into the upper part of the distillation column (not shown).

The oil bath temperature is raised to 125 DEG C and the EA / ethanol azeotrope (4) is continuously distilled.

Adjust the pressure at the top of the column so that the temperature inside the reactor does not exceed 95 ° C.

In this step, the pressure varies from 631 to 324 mbar and 166 g of EA / ethanol azeotropic material containing 69% by weight of ethanol are recovered. The reaction time is 3 hours.

Crude reaction product 5 (weight 652 g) has the following weight composition:

- EA: 20.5%

- 2-PH (isomeric total): 0.27%

- 2PHA (isomeric total): 78.47%

- catalyst + stabilizer + impurity: 0.76%

The crude reaction product is stored in buffer tank B which is continuously fed to the upper distillation column (C1) via stream 6.

Column C1 is a column containing stacked packings of the Multiknit type with seven theoretical plates operating under reduced pressure and with heat exchanger of the thermal siphon type. A mixture containing 500 ppm of HQME in EA is introduced into the upper part of the distillation column C1 (not shown).

Column C1 operates under vacuum (20-30 mbar, 100 < 0 > C maximum) to separate:

- At the top, stream 7 containing 99.5% of EA (138 g / h); And

- At the bottom, crude 2PHA (514 g / h) of the following composition: Stream 8:

EA: 0.1%

2-PH (isomeric total): 0.25%

2PHA (isomeric total): 98.69%

Catalyst + stabilizer + impurity: 0.96%

Stream 7 of EA is sent to the intermediate tank (not shown in the figure) to be recycled to the reaction.

Stream 8 of crude 2PHA is continuously sent (10 mbar, 160 ° C) to a film evaporator E operated under reduced pressure.

The film evaporator separates the following:

- At the top, purified 2PHA (463 g / h) stream 9 of the following composition:

2PHA (isomeric total): 99.57%

EA: 0.15%

2-PH (isomeric total): 0.27%

HQME Stabilizer: 250 ppm

In the bottom, stream 10 containing heavy by-products and catalyst (52 g / h), which is recycled to part 11, optionally for reaction, and the remainder being discarded.

Example 2 (for comparison)

The same synthesis as in Example 1 was carried out using butyl titanate as the catalyst.

In this case, EA overhead stream 7 from column C1 contains 10% butyl acrylate (BuA), which makes it unsuitable for recycling in this state during the reaction step, and for EA separation from butyl acrylate Additional distillation columns are required.

Example 3 (for comparison)

The same synthesis as in Example 1 was carried out using 2-ethylhexyl titanate as the catalyst.

In this case, the purity of 2PHA in stream 9 over the film evaporator is only 97.5%, because of the presence of 2-ethylhexyl acrylate. The grade of 2PHA does not provide the same performance in pressure sensitive adhesives such as 2PHA with a purity of 99.5%.

Claims (10)

Propylheptyl acrylate by a transesterification reaction of a hard alkyl acrylate and 2-propylheptanol in the presence of an alkyl titanate as a transesterification catalyst and at least one polymerization inhibitor, a high purity 2-propylheptyl acrylate Continuously withdrawing an azeotropic mixture composed of a light alkyl acrylate and a light alcohol produced by a transesterification reaction during the reaction and purifying the reaction mixture,
The catalyst is selected from ethyl titanate and 2-propylheptyl titanate in a solution of 2-propylheptanol;
-Product 2-propylheptyl acrylate as a crude reaction mixture comprising unreacted hard alkyl acrylate as a light product and a trace amount of 2-propylheptanol and a catalyst as a heavier product, polymerization inhibitor (s) Is conveyed under reduced pressure to distillation column (C1) and distillation is carried out in said column (C1) to obtain
At the top, a stream consisting essentially of unreacted light alkyl acrylate and a minor amount of 2-propylheptanol, and
o a stream essentially consisting of the desired 2-propylheptyl acrylate and catalyst, polymerization inhibitor (s), also the heavy reaction by-products, and traces of hard compound; after
Transferring the bottom stream from the distillation column (C1) to the film evaporator (E) under reduced pressure,
o At the top, the desired pure 2-propylheptyl acrylate; And
o In the bottom, the catalyst, polymerization inhibitor (s), and also heavy reaction by-products. The process according to claim 1, wherein the catalyst is ethyl titanate in a 2-propylheptanol solution. 3. Method according to claim 1 or 2, characterized in that it is carried out in a batch, continuous or semi continuous mode, preferably semi-continuous mode. 4. Process according to any one of claims 1 to 3, characterized in that the 2-propyl heptanol is a mixture comprising:
- 70 to 99%, preferably 80 to 95% of 2-propylheptanol n C ₅ H ₁₁ CH (C ₃ H ₇ ) CH ₂ OH and
Methyl-2-propyl-hexanol C ₂ H ₅ CH (CH ₃ ) CH ₂ CH (C ₃ H ₇ ) CH ₂ OH and 5-methyl- 2-propyl hexanol _{CH 3 CH (CH 3) CH} 2 CH 2 CH (C 3 H 7) CH ₂ OH in the mixture. 5. The method according to any one of claims 1 to 4, wherein the hard alkyl acrylate is ethyl acrylate. 6. A process according to any one of claims 1 to 5, characterized in that the film evaporator is a falling film evaporator or a wiped film evaporator. 7. Process according to any one of claims 1 to 6, characterized in that the upper stream of the column C1 is recycled to the reaction. 8. A process according to any one of the preceding claims, characterized in that the separated stream at the bottom of the film evaporator is recycled at least in part to the reaction. 9. A process according to any one of claims 1 to 8, characterized in that an azeotrope consisting of a light alcohol and a light alkyl acrylate produced in the transesterification reaction is recycled to a unit for the synthesis of a light alkyl acrylate. 10. The process according to any one of claims 1 to 9, wherein the polymerization inhibitor is hydroquinone monomethyl ether (HQME).

Images